Enhanced Mixed-Excitation Linear Prediction
Adaptive Digital's enhanced-MELP (MELPe) Federal Standard, is a low bit rate vocoder supporting 2400, 1200 and 600 bps.

MELPe

Mixed-excitation linear prediction (MELP) is a United States Department of Defense speech coding standard used mainly in military applications and satellite communications, secure voice, and secure radio devices. MELPe is an enhanced version of that codec.

FEATURES

  1. Functions are C-callable
  2. Multiple channel capable
  3. Optional noise preprocessing

Enhancements include: Noise preprocessing for removing background noise.

Coding Rate: 2400, 1200, and 600 bps

Sampling Rate: 8 kHz

AVAILABILITY

ADT MELPe is available on the following Platforms: Other configurations are available upon request.

Platform
ARM Devices - Cortex A8 / A9 / A15, Cortex - M4, [Cortex-M4 Preliminary], ARM9e/11*

* These Melpe libraries are available in 3 different Build configurations:

  1. Rate2400/Rate1200/Rate600  (all three) With Noise Pre-Processing (NPP)
  2. Rate2400/Rate1200 with NPP
  3. Rate2400 (only) with NPP

DESCRIPTION

Adaptive Digital’s MELPe - Enhanced version of MELP, a low bandwidth Federal Standard, robust in challenging background noise environments such as those frequently encountered in military communication systems.

Applications include Voice-Over-Packet, Satellite, and other digital voice applications.

MELPe vocoder is also known as military standard MIL-STD-3005 and NATO STANAG 4591

FRAME SIZE

The Melpe coder frame size is dependent on the Encode/Decode rate

Rate Frame Size (Samples) Frame Size (msec.)
600 bps 720 90 .0
1200 bps 540 67.5
2400 bps 180 22.5

SPECIFICATIONS


ARM®DEVICES

MELPe ARM Cortex-A8 / A9 / A15

CPU UTILIZATION
MIPS MIPS (600bps) MIPS (1200 bps) MIPS (2400 bps)
Nonlinear Preprocessor (NPP) 14 14 14
Encoder 46 44 27
Decoder 17 17 17

 

 

MELPe ARM Cortex-M4 (Preliminary)

CPU UTILIZATION
MIPS MIPS (600bps) MIPS (1200 bps) MIPS (2400 bps)
Nonlinear Preprocessor (NPP) < 30 < 30 < 30
Encoder < 60 < 50 < 50
Decoder < 30 < 30 <25
Total <120 <110 <105
--------------------------------------------------------------------------
MEMORY REQUIREMENTS

All Memory usage is given in units of byte.

Cortex-M4 Program Channel Scratch Tables Data
Encoder 100k 6560 6984 148k 63k
Decoder 1376
NPP 11968

 


MELPe ARM9e

CPU UTILIZATION
MIPS MIPS (600bps) MIPS (1200 bps) MIPS (2400 bps)
Nonlinear Preprocessor (NPP) 35 35 35
Encoder 493 489 81
Decoder 27 27 27


We specify MIPS (Millions of Instructions per Second) as MCPS (Millions of Instruction Cycles per Second). Unless otherwise specified, peak MIPS are indicated.

FUNCTION

API function call summary

MELPE_ADT_initEncode (…) Initializes the MELPe encoder
MELPE_ADT_initDecode (…) Initializes the MELPe decoder
MELPE_ADT_encode (…) Executes the MELPe encoder
MELPE_ADT_decode (…) Executes the MELPe decoder
NPP_ADT_init (…) Initializes the Melpe noise pre-processor
NPP_ADT_process (…) Executes the Melpe noise pre-processor

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Mixed-excitation linear prediction (MELP) is a United States Department of Defense speech coding standard, traditionally used in military applications, secure voice, and radio devices.

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